Neurons/Neurotransmitters WEEK 5 Flashcards
PNS
Periphereal Nervous System
The branches that come out off the axon are called
Axon Terminals
CNS
Central Nerous System
PNS contains
all neural structures that are outside the brain and spinal cord
Two main functions of the PNS
Input and out put functions
Input function of PNS
sense whats going on inside and outside the body
Output function of PNS
Allows you to react/response through muscles and glands
PNS- Somatic Nervous System SNS (part of PNS)
Ability to sense and respond to environment, mechanic in the body that allows that to happens
Make up of PNS
Somatic Nervous System PNS *****
The somatic nervous system contains sensory neurons
This study has moved away from looking at specific areas and now to
Networks
The brain is constantly producing —— even in adulthood and post debvelopment
cells
Neuron two main areas
Cell Body - soma
and the Axon
Neuron collect messages for the —- from neighbouring nurons
Soma
Genetic material in the nucleus of a neuron shapes —-
function
Insulating membrane controls the exchange of chemical substances in an out of the cell
Myelin Sheath
The centre of the soma or neuron is called the
Nucleus
The branch off the soma of a neron (insulated by the myelin sheath) is called the
Axon
Neurons require — to stay alive
biochemical structures
The branches that come out off the soma are called
Dendrites
Nueron axons conduct electrical impulses to
Other neurons/glands/muscles
Having many axon terminals allows a neuron to
permit a single neuron to pass messages to thousands of neurons
the transmission of neurotransmitters across the cell membrane can be measured and is important because it grants us the ability to use disgnostics such as
EEG etc in order to look at neural firing
Action potential is built up during
the transmission of neurotransmitters across the cell membrane
Action potential builds up and fires an impulses down the axon which allows for
interconnection between all areas of the brain
Nuerons are general local, they are not
long distance communication devices
most neurons talk to each other within a
hemisphere
Neurons are the
basic building blocks of the nervous system
Extimated 100 billion or trillion nueronsEsimated number of neurons we have is
upwards of 100 billion if not trillions
The cells that provide support for the neurons are called
Glial cells
Imagine a chocolate chip cookie, if the nurons are the chocolate chip the cookie is the
Glial cells
Glial cells
hold neurons in place, manufacture nutrient chemicals and absorb toxins and waste
Neurons generate —- and this creates ——- which ——-
Neurons generate electricity, and this creates nerve impulses (to fire action potentials down the line)
Neurons release chemicals that
facilitate communication and do various things
A neuron begins at —— resting potential
negative
The cell membrane of a neuron encloses
cytoplasm
The cytoplasm of a cell contains
Various Ions dissolved in it
neurons themselves are immersed in a salt solution called
Extracellular fluid
The ions of the cytoplasm consist mainly of positively charged potassium ions and large —– —— —– ——
negatively charged organic molecules (such as proteins)
Extracellular fluid contains
mostly positively charged sodium ions and negatively charged chloride ions
Unstimulated, neurons maintain a constant electrical difference or “potential” across their cell membrane called
resting potential
The potential called resting potential is always —- inside the cell
negative (-40 to -90 millivolts)
The negative potential inside the neuron can be made —– or —- negative depending on the —–
more or less negative depending on the stimulus
If potential is made less negative it reaches a level called
Threshold and an action potential is triggered
During action potential the neuron suddenly becomes
20 - 50 milivolts positive inside (lasting a few millisecond)
After action potential is triggered the
cell restores its negative resting potential
since chraged particles cannot pass through the lipids that make up cell membranes
they must travel through channel protiens that extend through the membrane
In an unstimulated neuron only —– ions can cross the membrane
potassium
potassium ions, travel through specfic protiens called
potassium channels
Although sodium channels are also present in unstimulated nureon they are
closed
since only potassium ions can cross the membrane and are more concentrated inside the call
they diffuse out ofthe cell, leaving the large organically charged ions behind
As the potassium ions leave the cell, the inside of the cell becomes increasing
negative
because opposite charges attract, as potassium ions an electrical force develops that tends to pull them
back inside the neuron
At some point the diffusion of potassium ions outside the neuron due to concentration difference is balanced by the electrical attraction tending to pull them back inside, this is the point at which neurons reach
Resting potential
Reaching resting potential in this way does not require significant changes in
potassium concentration inside or outside the cell (only about 1/10,000 of the potassium ions initially inside a neuron must leave to create a resting potential of -60 millivolts
action potentials (not resting potentials) do what:
carry information through a nervous system
3 steps in the Activations of nerve impulses (nuerall impulse/action potential)
- Electronic Resting potential
- Neuron is stimulated and Action potential occurs
- Original ionic balance is restored, and the neuron returns to resting potential
There is a —– period where the neuron is silent and wont fire again for a period of time or until the threshold is built up again
refractory
Neuron is seperated from surrounding fluid by a
cell membrane
Substances can pass through a cell membrane using designated
ion channels
Inner ions are more negatively charged than the
surrounding ions
When a neuron is at rest it is
negatively charged
Positive sodium ions enter a neuron causing brief
depolarisation
the action of positively charge sodium ions entering the call membrane and causing depolarisation between the negaively and positively charged ions is what we measure using
EEG for example
Action potential is
the electrical shift when a neuron is stimulated
Resting potential….sodium flows in …. causing depolarisation between negative and positive, which will affect or reach the
Action potential Threshold
Once the action potential threshold is reached this triggers an
Action potential
After an action potential threshold is reached and thus the action potential is triggered the ——- ions flow ou
the potassium ions flow out
After an action potential, the potassium ions flow out which causes
Repolarisation (of the ions)
After and action potential and repolarisation of the ions a neuron will have a brief
refractory period where it remains silent until restimulated
After an action potential and before a return to resting potential, the neuron will have a brief
refractory period then return to resting potential
An action potential usually occurs in what measure of time
millisecond
Action potential threshold begins to come into play as the
neuron depolarises (the charge builds up in the neuron, potassium ions enter)
the charge builds up in the neuron because
potassium ions enter
The neuron cannot fire until it regains natural negative resting polarisation, this is achieved by the
Absolute refractory period
All or none law of a neuron
Action potential occur either at a uniform (maximum) intensity or not at all. Binary. (if it doesnt build up past the threshold, it just returns to its resting state, it does not fire at all. You do not get a weak or stong firing, you get firing or no firing)
Can a neuron transmit a weak signal if it does not reach the action potential threshold
No, An action potential either fires or it does not. If the Action potential is not reach, nothing happens.
We can have a summation of graded potential (charge below action potential threshold) come together to reach
Action potential threshold - trigger an action potential
Any change to resting potential that doesnt reach action potential thershold is called
Graded potential
Rules of Nureons
All or none
Action potential Threshold
Graded potential
We can have grade potentials (any charge) coming together to summatie into
firing (in certain circumstances)
Stochastic / Stochaticity
the quality of lacking any predictable order or plan. haphazardness, randomness, noise, irregularity - not characterized by a fixed principle or rate; at irregular intervals.
the threshold is not neccessarily always the
same (either graded potentials can add up or the thresholds can change and thus whether a neuron fires or not can actually be seen as a probabilistic function)
——- ——- refers to a function or process that involves randomness or uncertainty in its outcomes. Often used to model complex and uncertain behaviors.
probabilistic functions
Whether a neuron fires or not may be viewed as a
probabilistic function ( a function or process that involves randomness or uncertainty in its outcomes, often used to model complex and uncertain behaviours.)
Bayesian probability
is an interpretation of the concept of probability, in which, instead of frequency or propensity of some phenomenon, probability is interpreted as reasonable expectation representing a state of knowledge or as quantification of a personal belief. (ie. Bayesian probability is like using your personal knowledge and beliefs to make predictions, taking into account the information you have at the moment. It’s a way to put numbers to what you think is likely to happen based on what you know.)
Neurons touch each other, true or false
False (neurons do not touch)
Axon terminals and dendrites (branches of the soma) do not touch the space between (small interstitial space) them is called the
Synaptic space
Chemical substances that carry messages across the synaptic space to other muscles, neurons or glands are called
Neurotransmitters
The axon has branches to send the messages called axon terminals and at the send of each of these axon terminals is a
synaptic terminal